Cigarette smoking is a major risk factor for cardiovascular disease. We have previously documented abnormalities in the excretion of urinary metabolites of thromboxane B2 and prostacyclin, major products of arachidonic acid metabolism in platelets and endothelial cells in apparently healthy cigarette smokers. Despite such evidence consistent with platelet activation in vivo, the response of chronic smokers' platelets to aggregating agonists ex vivo was depressed. The present studies extend these observations. In Specific Aim 1 we will study the effects of quitting smoking on eicosanoid formation, relate the abnormality to an independent index of platelet function in vivo (radiolabelled platelet turnover) which is reportedly abnormal in smokers and examine the effects of reinstitution of smoking after short term withdrawal. These studies are designed to relate smoking to biochemical evidence of a reversible pathology. In Specific Aim 2 we shall examine the human pharmacology of nicotine, a constituent of cigarette smoke, in some detail. The rationale for selecting nicotine for particular attention is provided by studies which suggest that it modifies eicosanoid formation by vascular tissues in vitro. In Specific Aim 3 we address the direct effects of smoking on platelets at both the cellular and molecular levels which might explain the hyporesponsiveness to aggregating agonists which we have observed ex vivo. In Specific Aim 4 we take advantage of recent technological advances to study the effects of smoking on the formation of both lipoxygenase and cyclooxygenase products at the platelet-vascular interface in vivo in man. Additional experiments will examine the effects of products of both the aqueous and nonaqueous components of cigarette smoke and of plasma from chronic smokers on the biochemistry and morphology of pulmonary endothelial cells and their interaction with neutrophils and platelets in vitro. Finally, in Specific Aim 5 we shall utilize our ability to monitor indices of the major pathways of thromboxane and prostacyclin metabolism to discriminate between an effect of smoking on the biosynthesis of these eicosanoids from an effect on their metabolism and to assess the dose-response relationship. We shall also address the hypothesis that pulmonary cells, particularly the alveolar macrophage, may contribute, together with the platelet, to the increment in metabolite excretion observed in chronic smokers.